To reproduce run attached file.
This bug is reproducible on Windows 7 with b99.

Run log:
Uncaught exception on thread : Thread[JavaFX Application Thread,5,main]
java.lang.NullPointerException
at javafx.embed.swing.SwingNode.locateLwFrame(SwingNode.java:425)
at javafx.embed.swing.SwingNode.access$800(SwingNode.java:105)
at javafx.embed.swing.SwingNode$8.invalidated(SwingNode.java:329)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:339)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyDoubleWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyDoubleWrapper.java:177)
at javafx.beans.property.ReadOnlyDoubleWrapper.fireValueChangedEvent(ReadOnlyDoubleWrapper.java:143)
at javafx.beans.property.DoublePropertyBase.markInvalid(DoublePropertyBase.java:113)
at javafx.beans.property.DoublePropertyBase.set(DoublePropertyBase.java:146)
at javafx.stage.Window$1.setLocation(Window.java:91)
at com.sun.javafx.stage.WindowHelper.setLocation(WindowHelper.java:48)
at com.sun.javafx.stage.WindowPeerListener.changedLocation(WindowPeerListener.java:49)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:67)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:39)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:130)
at com.sun.glass.ui.Window.handleWindowEvent(Window.java:1241)
at com.sun.glass.ui.Window.notifyMove(Window.java:1165)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:101)
at java.lang.Thread.run(Thread.java:724)